1. Field of the Invention
The present invention relates generally to a mobile radio communication system, and in particular, to a method for processing data by varying the power and bit rate according to a channel condition between a base station and a mobile station and the required quality of service (QoS).
2. Description of the Related Art
The IS-95 standard supports a real-time voice data service which is called a circuit service. Circuit services can be viewed as a special case of packet services in the sense that dedicated traffic and control channels are typically assigned to the mobile station for extended periods of time during circuit service sessions. This will lead to less efficient use of the air interface capacity. However, some delay sensitive services such as video applications require a dedicated channel for the duration of the call. The circuit service may be characterized in that it sends input circuit data consecutively. In contrast to the IS-95 standard, a mobile communication system based on the IMT-2000 standard, supporting a high bit rate, can provide a packet data service for large quantity data, such as a moving picture and an image, using a supplemental channel. The packet data is transmitted as inconsecutive burst data, whereas the circuit data based on the IS-95 standard is transmitted as consecutive voice data. Further, for the packet data service defined by the IMT-2000 standard, it is required to maximize throughput while satisfying various bit rates required by users. In contrast, in the IS-95, for the voice server, it is required to provide a uniform service to all the users irrespective of the channel condition. To satisfy the IS-95 uniform service requirement, the system allocates higher power to a mobile station under a bad channel condition. However, such a method cannot be used to maximize the data throughout for the packet data service.
When the consecutive data processing method for the circuit service is applied to the packet service which transmits data inconsecutively, it is difficult to maximize a bit rate of the packet data, thus causing a decrease in data processing efficiency and channel efficiency.
In addition, the aforementioned data processing problem occurs even during a handoff. That is, a handoff method in an existing mobile communication system providing the circuit service combines or selects the same data transmitted simultaneously from at least two mobile stations concerned in the handoff. When this handoff method is applied to the packet service, it is difficult to adaptively optimize a bit rate according to the channel condition, thus causing a reduction in packet throughput. Therefore, to provide a packet data service, the data transmission method and the handoff method should be redesigned to satisfy transmission characteristics of the packet data. In particular, there is required a new method for allocating power of the forward link to a mobile station and establishing a data path passing through the base station.
It is, therefore, an object of the present invention to provide a data processing method for packet data communication in a mobile communication system, in which a mobile station estimates a channel condition using a signal transmitted from a base station and transmits channel status information to the base station, and the base station then allocates higher power for a mobile station in a good channel condition depending on the channel status information and transmits data to the mobile station with the allocated power.
It is another object of the present invention to provide a data processing method for packet data communication in a mobile communication system, in which a mobile station estimates a channel condition using a signal transmitted from a base station and transmits channel status information to the base station, and the base station then transmits data to a mobile station in a good channel condition at a higher bit rate depending on the channel status information.
It is further another object of the present invention to provide a data processing method for packet data communication, wherein a mobile station transmits channel status information to a base station, and receives data with rate indicator that the base station has transmitted in response to the channel status information, so as to rapidly adapts to a variable bit rate.
It is still further another object of the present invention to provide a data processing method for packet data communication in a mobile communication system, wherein a mobile station determines a bit rate and power depending on a weighting factor corresponding to the type of service data.
It is still further another object of the present invention to provide a data processing method for packet data communication in a mobile communication system, wherein to maximize throughput of packet data during a handoff, a base station controller transmits divided different data to base stations concerned in the handoff, and the base stations receive channel status information and transmit packet data to a mobile station only when a channel is in a good condition.
It is still further another object of the present invention to provide a data processing method for packet data communication in a mobile communication system, wherein to maximize throughput of packet data during a handoff, a base station controller transmits the same data to base stations concerned in the handoff and the base stations receive channel status information and transmit packet data to a mobile station only when a channel is in a good condition.
In order to accomplish the above objects, there is provided a packet data processing device for a mobile communication system. A base station includes a channel status information receiver for receiving channel status information for a forward channel from a mobile station; a supplemental channel transmission controller for determining a bit rate of the mobile station according to the channel status information, a supplemental channel transmitter for transmitting data to the mobile station at the bit rate determined by the supplemental channel transmission controller; and a rate indicator transmitter for generating a rate indicator having information about the determined bit rate and transmitting the generated rate indicator to the mobile station. The mobile station includes a channel status measurer for detecting power of a signal received over a pilot channel to measure channel status; a channel status information transmitter for generating channel status information according to the measured channel status and transmitting the channel status information to a base station; and a supplemental channel receiver for detecting a bit rate of data transmitted at a variable rate from the base station and receiving data at the detected bit rate.